Typically, most speckle reduction techniques rely on the use of an image plane or a relayed image of the source. A time-averaging diffuser wheel is a common way to average speckle, but it acts as a random array of scatter centers, maintaining x-y position of the beam while redistributing the angular content of the beam over time to average multiple differing speckle patterns over time. Thus, on average, the beam intensity can be measured across x-y position with reduced impact of interference effects of speckle. Angular Diversity is discussed in many references as a way to mitigate speckle. Angular Diversity involves maintaining x-y position of a spot in image space while changing its angular properties over time.
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